This invention relates, in general, to a method of forming electrical inductance coils and the electrical coils formed thereby particularly useful in providing the rotating in-plane magnetic field for the propagation of bubbles in bubble memories.
As stated in the Layton et al Application, supra, there are a number of prior patents relating to the formation of coils of various types and the method and coil disclosed and claimed in the prior Application met the requirements for a coil having a high packing coefficient, at reduced cost with a choice of design of the coil, such as for example, changing the pitch of the coils to vary the induced magnetic field strength and to change the distributed capacitance of the coil.
This invention is directed to further improving the coil disclosed and claimed in the prior Application by improving the uniformity of the field induced by the coil and improving the magnetic efficiency thereof.
It is apparent that, in the coil formed as taught by the prior Application, the spacing of the conductors from one another in the plane of the substrate, induces a non-uniform magnetic field in the center of the coil, i.e., there are valleys and dwells in the magnetic field strength at the center plane of the coil. The present invention, on the other hand, utilizing conductors formed on both sides of the substrate and arranged such that the conductors on one side overlap the spacing between the conductors on the other side, will induce a uniform magnetic field in the plane of the coil when a current flows therethrough. Spacing of coils to provide such a coil utilizing printed circuit board techniques and providing a flat coil having a high packing coefficient at a reduced cost and allowing a choice of design is most difficult to solve but solved by the method taught herein.
Accordingly, it is a primary object of this invention to provide a new and improved method of forming a magnetic coil having improved magnetic characteristics over the prior art coils and to form a coil utilizing printed circuit board techniques.